1. Field of the Invention
The present invention relates to liquid dispensing equipment, and, more particularly, to suspension systems for such equipment.
2. Description of the Related Art
For many years, liquid dispensing equipment has been part of the agricultural field. The liquid dispensing equipment is used to distribute liquid fertilizer and/or insecticides or herbicides onto the ground of a field for agricultural purposes. Usually, such equipment takes the form of a mobile wheeled vehicle with significant clearance height so as to clear crops that have partially matured. The equipment usually consists of a power unit for self propulsion, an operator cab and a liquid reservoir. Liquid is dispensed using articulated booms that are retracted for transport to the field and then extended laterally to distribute the liquid onto the field.
One of the requirements of such a device may be to have a controllable, substantially constant, suspension travel so that the equipment, and thus the spray boom, is at a constant level above the field surface. This is done to ensure uniform distribution and coverage of the material being sprayed.
Many liquids solutions utilize water as a base and are thus relatively dense. As a result, the full and empty weight of the equipment is substantially different and this could be reflected in the variation of suspension travel, thus producing inconsistent coverage.
In an attempt to counter this effect, active suspension systems have been proposed similar to suspension systems in the automotive field. These include a suspension strut mounted within suspension springs and operable, through pressurized hydraulic fluid, to raise or lower the suspension travel. In the prior art, suspension systems have utilized relatively expensive components to physically measure the distance of the frame from the field thus reflecting suspension travel. With systems of this type there is a significant cost of the sensor components and the potential of exposure to the debris and other material normally experienced when traversing a field.
Accordingly, it is an object of the present invention to provide a simplified and reliable way to provide an active suspension for liquid dispensing equipment.